1. fetch('flowers.jpg').then(function(response) {
    2.   if(response.ok) {
    3.     return response.blob();
    4.   }
    5.   throw new Error('Network response was not ok.');
    6. }).then(function(myBlob) { 
    7.   var objectURL = URL.createObjectURL(myBlob); 
    8.   myImage.src = objectURL;
    9.   downloadFileByBlob(objectURL, 'flowers.jpg');
    10. }).catch(function(error) {
    11.   console.log('There has been a problem with your fetch operation: ', error.message);
    12. });
    14. function downloadFileByBlob(blobUrl, filename) {
    15.   const eleLink = document.createElement('a');
    16.   eleLink.download = filename;
    17.   eleLink.style.display = 'none';
    18.   eleLink.href = blobUrl;
    19.   // 触发点击
    20.   document.body.appendChild(eleLink);
    21.   eleLink.click();
    22.   // 然后移除
    23.   document.body.removeChild(eleLink);
    24. }